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United States Patent |
5,041,917
|
Koshiishi
|
August 20, 1991
|
Facsimile apparatus adapted to communicate via more than one
transmission medium each having different transmission quality
Abstract
A facsimile apparatus comprises a modem, a communication controller, an
image reader, an image recorder, and a system controller, wherein the
system controller comprises a first medium discriminating part for
discriminating the type of the transmission medium used, an error
detection part for detecting a transmission error upon reception of the
received image data on the basis of a predetermined error detection
standard, an error detection reference part for setting the predetermined
error detection standard in accordance with type of the transmission
medium discriminated by the first medium discriminating means, error
reporting means for controlling the communication controller such that an
error signal indicative of a transmission error is transmitted to another
facsimile apparatus, and a second medium discriminating part for
controlling the communication control means such that the type of the
first transmission medium is reported to said another facsimile apparatus.
Inventors:
|
Koshiishi; Takaho (Tokyo, JP)
|
Assignee:
|
Ricoh Company, Ltd. (Tokyo, JP)
|
Appl. No.:
|
482839 |
Filed:
|
February 21, 1990 |
Foreign Application Priority Data
Current U.S. Class: |
358/434; 358/435; 358/436; 358/445; 379/33; 379/100.06 |
Intern'l Class: |
H04G 001/32 |
Field of Search: |
358/405,434,435,436,437,438,439,443,445
379/32,33
|
References Cited
U.S. Patent Documents
4887162 | Dec., 1989 | Arai | 358/434.
|
4933770 | Jun., 1990 | DeSpain | 358/434.
|
4975783 | Dec., 1990 | Takaoka | 358/437.
|
Foreign Patent Documents |
59-41971 | Mar., 1984 | JP.
| |
Primary Examiner: Boudreau; Leo H.
Assistant Examiner: Fallon; Steven P.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt
Claims
What is claimed is:
1. A facsimile apparatus for transmitting and receiving a facsimile
transmission via a data transmission path including a first transmission
medium at an end thereof to which the facsimile apparatus is connected, to
and from another facsimile apparatus at the other end of the data
transmission path, said data transmission path including at the other end
thereof a second transmission medium selected from a plurality of
transmission media each of different type and including a transmission
medium identical to the first transmission medium, comprising:
modem means connected to the data transmission path for modulating an image
data to be transmitted by the facsimile transmission via the data
transmission path and for demodulating a received image data received by
the facsimile transmission from said another facsimile apparatus via the
transmission path;
communication control means coupled to the modem means for controlling the
transmission and reception of the facsimile transmission to and from said
another facsimile apparatus via the data transmission path;
reading means for reading an image to be transmitted and producing an image
data to be transmitted by the facsimile transmission in correspondence to
the image which has been read;
recording means for recording a visual image corresponding to an image data
included in the received facsimile transmission; and
system control means for controlling operations of said communication
control means, said reading means and said recording means;
said system control means comprising first medium discriminating means for
discriminating the type of the second transmission medium, error detection
means for detecting a transmission error upon reception of the received
image data on the basis of a predetermined error detection standard, error
detection reference means for setting the predetermined error detection
standard on the basis of which the error detection means performs the
detection of the transmission error, said error detection reference means
changing the predetermined error detection standard upon the type of the
second transmission medium discriminated by the first medium
discriminating means, error reporting means for controlling the
communication control means such that an error signal indicative of a
transmission error is transmitted to said another facsimile apparatus, and
second medium discriminating means for controlling the communication
control means such that the type of the first transmission medium is
reported to said another facsimile apparatus.
2. A facsimile apparatus as claimed in claim 1 in which said first medium
discriminating means discriminates the type of the second transmission
medium based on a signal transmitted from said another facsimile apparatus
together with the facsimile transmission.
3. A facsimile apparatus as claimed in claim 2 in which said signal it is
transmitted together with a predetermined procedure signal of facsimile
transmission transmitted from said another facsimile apparatus for
informing of conditions on which the facsimile transmission will be made.
4. A facsimile apparatus as claimed in claim 3 in which said signal is
transmitted as a part of the predetermined procedure signal.
5. A facsimile apparatus as claimed in claim 1 in which said second medium
discriminating means controls the communication control means such that a
signal is transmitted to said another facsimile apparatus informing of the
type of the first transmission medium.
6. A facsimile apparatus as claimed in claim 1 in which said communication
control means transmits the signal together with the facsimile
transmission to said another facsimile apparatus.
7. A facsimile apparatus as claimed in claim 1 in which said communication
control means transmits the signal together with a predetermined procedure
signal of facsimile transmission for informing said another facsimile
apparatus of a condition under which the facsimile transmission will be
made.
8. A facsimile apparatus as claimed in claim 1 in which said communication
control means transmits the signal as a part of the predetermined
procedure signal.
9. A facsimile apparatus as claimed in claim 1 in which said error
detection means counts up the number of lines that involved errors in one
page of the image transmitted by the facsimile transmission and detects
the transmission error when the number has reached a predetermined number
of lines set by the error detection reference means as the predetermined
error detection standard, and said error detection reference means sets
the predetermined number of lines to a first value when it is
discriminated by the first medium discrimination means that the second
transmission medium is identical to the first transmission medium and to a
second value different from the first value when it is discriminated by
the first medium discrimination means that the second transmission medium
is different from the first transmission medium.
10. A facsimile apparatus as claimed in claim 9 in which the first
transmission medium provides a first transmission quality while the second
transmission medium provides a second transmission quality lower than the
first transmission quality, and the first value of the predetermined
number of lines is set lower than the second value of the predetermined
number of lines.
11. A facsimile apparatus as claimed in claim 10 in which error detection
means further detects, when it is discriminated by the first medium
discriminating means that the second transmission medium is not identical
to the first transmission medium, the transmission error by monitoring the
line involving errors appearing successively for a third value of the
predetermined number of lines set lower than the second value of the
predetermined number of lines.
12. A facsimile apparatus as claimed in claim 1 in which said first
transmission medium is selected from the plurality of transmission media
each of different type and said second medium discriminating means
comprises a detector means for detecting the type of the transmission
medium used as the first transmission medium
13. A facsimile apparatus as claimed in claim 12 in which said plurality of
transmission media comprises an automobile telephone network.
14. A facsimile apparatus as claimed in claim 12 in which said plurality of
transmission media comprises an acoustic coupler.
15. A facsimile apparatus for transmitting and receiving an image data via
a transmission path including a transmission medium selected from a
plurality of transmission media, comprising:
modem means connected to an end of the transmission path for modulating a
transmitting image data to be transmitted via the transmission path and
for demodulating a received image data transmitted via the transmission
path;
communication control means coupled to the modem means for controlling the
transmission and reception of the facsimile transmission to and from the
data transmission path;
image reading means for reading a document image to be transmitted and for
producing the transmitting image data corresponding to the document image
that has been read;
image recording means for recording a visual image in accordance with the
received image data on a recording sheet;
system control means for controlling operations of said communication
control means, said reading means and said recording means;
said system control means including medium discrimination means for
discriminating the transmission medium included in the transmission path,
error detection means for counting up errors involved in the received
image data and detecting a transmission error when a number of the counted
errors has exceeded a predetermined threshold, error detection reference
means for setting the predetermined threshold, said error detection
reference means changing the predetermined threshold in response to the
discrimination by the medium discrimination means, and means for informing
of the transmission error to a terminal transmitting the facsimile
transmission from another end of the transmission path.
Description
BACKGROUND OF THE INVENTION
The present invention generally relates to facsimile apparatus and more
particularly to a facsimile apparatus adapted to communicate via more than
one transmission medium each having different transmission quality.
In the commonly used facsimile communication system designed according to
the CCITT G3 standard, a facsimile apparatus in the source terminal
transmits a PIX signal representing a coded image data for one page
document, and when this is completed, sends an EOP signal indicative of
end of transmission of that page. In the destination terminal, a facsimile
apparatus receives the PIX signal sequentially, and decodes the
transmitted image from the PIX signal thus received In this process of
decoding, occurrence of transmission error is monitored in each line.
In the conventional facsimile communication procedure, the facsimile
apparatus at the destination terminal returns a signal commonly designated
as an RTN signal to the source terminal when the detected transmission
error has exceeded a predetermined threshold. The discrimination is made
usually when the number of transmitted lines that involved the
transmission error has reached a predetermined number such as ten. In
response to this RTN signal, the facsimile apparatus in the source
terminal terminates the transmission by sending a DCN signal indicative of
disconnection of facsimile transmission. At the same time, the facsimile
apparatus in the source terminal displays a message such as "RE-SEND THE
DOCUMENT" and requests the re-transmission of document to the operator at
the source terminal.
In recent years, facsimile communication is made not only between facsimile
apparatuses at offices via wired transmission line in which a high
transmission quality is guaranteed but also between a facsimile apparatus
at a fixed station such as in an office and a facsimile apparatus at a
mobile station such as on an automobile, or between two mobile stations
via a wireless or radio transmission line. The term "wired transmission
line" used herein means a transmission line such as public telephone
network wherein a high transmission quality is guaranteed and may involve
radio transmission path wherein a high transmission quality is guaranteed
such as microwave transmission path or satellite transmission path
therein. On the other hand, the phrase "wireless transmission line" means
a transmission line such as automobile telephone network which provides a
communication service with a lesser transmission quality. Further, there
is recently developed a portable facsimile apparatus which can be
connected to the public telephone network via an acoustic coupler. When
using this portable facsimile apparatus, the acoustic coupler connected to
the facsimile apparatus is mounted on a handset of telephone apparatus and
the facsimile transmission is made in a form of acoustic signal exchanged
between the acoustic coupler and the telephone handset.
In such a newly developed facsimile communication system using the
transmission medium such as wireless transmission line or acoustic
coupler, the system is naturally vulnerable to noises and thus, there
occurs rather easily a case in which transmission error amounting several
tens of lines appears in one page document. When this occurs, the
conventional facsimile apparatus interrupts the facsimile transmission and
requests the operator to re-send the document. Thus, there arises a
problem that the operator has to carry out a number of trials in order to
send one document when the facsimile transmission is made via wireless
transmission line or via acoustic coupler.
This problem may be solved if the error detection at the destination side
facsimile apparatus is totally omitted and the destination receives the
facsimile transmission whatever the quality of the transmission may be.
However, such a measure is unacceptable as there is a substantial chance
that an entirely unintelligible document is transmitted without the
operator at the source terminal knowing the fact that the transmission is
failure and the transmitted image is unintelligible.
Thus, the conventional facsimile transmission system adapted for performing
facsimile transmission via more than one transmission medium suffers from
a problem that the facsimile transmission has to be repeated a number of
times in order to complete transmission of even one page of the document.
Otherwise, one has to accept poor quality of transmission in which a
substantial part of the document may be dropped or unintelligible.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a
novel and useful facsimile apparatus wherein the aforementioned problems
are eliminated.
Another and more specific object of the present invention is to provide a
facsimile apparatus adapted for facsimile communication via more than one
transmission medium each having different transmission quality, wherein
the number of trials to send a document in order to achieve a satisfactory
quality of transmission of the document is reduced, and wherein the
threshold to distinguish whether the facsimile transmission has a
satisfactory quality or not is changed in accordance with the type of the
transmission medium used. According to the present invention, a facsimile
transmission of reduced quality is accepted when the facsimile
transmission is made via a transmission medium having a poor transmission
quality although still maintaining a predetermined minimum quality of
facsimile transmission. Thereby, repetitive trial of transmitting a
document, otherwise would have to be made until a satisfactory
transmission is obtained, is avoided while at the same time maintaining a
certain quality of facsimile transmission. Only when it is discriminated
that the quality of transmission is poor with respect to the reduced
threshold quality or standard, a request is made to the operator at the
source terminal to re-send the document.
In one embodiment, discrimination of the transmission quality is made by
the number of error lines in one page document in which the transmission
error has occured. Thus, the foregoing threshold corresponds to the
allowable number of error lines involving the transmission error, and this
allowable number of error lines is changed in accordance with the type of
the transmission medium. Thus, the allowable number of error lines
involving the transmission error is increased when the transmission medium
having a poor transmission quality is used while the allowable number of
such lines is decreased when the transmission medium used has a high
transmission quality. The discrimination of the transmission quality
whether the transmission is acceptable or not may be made further on the
basis of continuous appearance of lines involving the transmission error.
In this case, the number of allowed error lines is kept small, as the
continuous dropout of lines makes the document easily unintelligible even
when the number of lines involving the error is small.
Other objects and further features of the present invention will become
apparent from the following detailed description when read in conjunction
with attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram showing a communication procedure commonly used in the
prior art facsimile system;
FIG. 2A is a block diagram showing a construction of a facsimile system
according to a first embodiment of the present invention;
FIG. 2B is a block diagram showing a facsimile apparatus loaded on an
automobile and the like and constituting a part of the system of FIG. 2A;
FIG. 3 is a diagram showing procedure signals transmitted at a start of
facsimile communication;
FIG. 4 is a diagram showing a structure of an NSS signal used in the
facsimile system of FIG. 2A for discriminating the type of transmission
medium used for facsimile communication;
FIG. 5 is a flowchart showing an error detection process performed in a
facsimile apparatus in FIG. 2A in the reception mode;
FIG. 6 is a block diagram showing a mechanism used in the facsimile system
of FIG. 2B for detecting that a facsimile apparatus is connected to a
mobile telephone set:
FIG. 7 is a block diagram showing a construction of a facsimile system in
which facsimile transmission is made via an acoustic coupler;
FIGS. 8A and 8B are flowcharts showing another error detection process
performed in the facsimile system of FIG. 2A; and
FIG. 9 is a flowchart showing a modified error detection process.
DETAILED DESCRIPTION
FIG. 2A shows a facsimile system in which a facsimile apparatus according
to a first embodiment of the present invention is used.
Referring to FIG. 2A, the facsimile system is used in a fixed station such
as office and comprises a fixed type facsimile apparatus 1 which in turn
comprises a scanner 11, a plotter 12, an encoding and decoding unit 13, a
communication controller 16, an operation/display unit 17, and a system
controller 18 coupled to each other via a system bus 10. Further, a modem
15 is coupled to the communication controller 16.
The scanner 11 reads a document image and outputs an image data with a
predetermined resolution in response to the reading of the document. The
image data thus obtained is supplied to the plotter 12 where the image
data is recorded onto a recording sheet in a form of a visual image. The
encoding and decoding unit 13 encodes the image data which is to be
transmitted to a facsimile apparatus at a destination terminal when the
facsimile apparatus 1 is used as a source terminal sending a facsimile
transmission. When the facsimile apparatus 1 is used for receiving a
facsimile transmission, the encoding and decoding unit 13 performs a
decoding of transmitted image data.
The modem 15 modulates a carrier by the image data to be transmitted to
form a modulated carrier when transmitting an image data and demodulates
the modulated carrier when receiving the image data to recover the
transmitted image data. Further, the modem 15 transmits various procedure
signals of transmission control procedure. The modem 15 is connected to a
network controller 14 which is physically connected to a public telephone
network 3 and the network controller 14 performs a predetermined automatic
calling and answering procedure. Thereby, a connection is established
between the facsimile apparatus 1 and another facsimile apparatus 2 at the
other end of the network 3.
The network 3 may be a wired telephone network commonly used for public
telephone communication or may be a network involving a wireless
transmission path as in the case of public automobile telephone network.
In the former case, the facsimile apparatus 2 at the other end of the
network 3 is used in another fixed station and may have a construction
similar to that of the facsimile apparatus 1 while in the latter case, the
facsimile apparatus is used in a mobile station provided in an automobile
and may have a construction shown in FIG. 2B.
FIG. 2B shows a mobile facsimile system 4 comprising a facsimile apparatus
41, wherein the facsimile apparatus 41 has a construction similar to that
of the apparatus 1 except that the network controller 14 is not used as
will be described layer with reference to FIG. 6. Thus, the facsimile
apparatus 41 is connected to an automobile telephone apparatus 43 via an
interface unit 42 provided for signal level adjustment or impedance
matching between the modem 15 and the automobile telephone apparatus 43.
The communication controller 16 controls the communication in the error
correction mode (ECM) of the group III standard recommended by the CCITT,
and makes a predetermined facsimile communication. The operation/display
unit 17 has an operation portion for setting various operations of the
facsimile apparatus 1 (or facsimile apparatus 41) and a display portion
for displaying modes of the facsimile apparatus 1 (or 41), guidance for
operating the facsimile apparatus 1 (or 41) and the like.
The system controller 18 comprises a microcomputer for example, and
controls the scanner 11, the plotter 12, the encoding and decoding unit
13, the communication controller 16 as well as the operation/display unit
17 so as to carry out a predetermined operation of the facsimile apparatus
1 (or 41).
FIG. 3 shows a sequence of procedure signals exchanged at the beginning of
the image transmission, after the connection between a source terminal and
a destination terminal is established.
Referring to FIG. 3, a facsimile apparatus at the destination terminal
sends sequentially a called station identification (CED) signal, a
non-standard facilities (NSF) signal and a digital identification signal
(DIS) all specified in the CCITT recommendation, wherein the CED signal
informs the source that the facsimile apparatus at the destination
terminal is ready to receive the transmission while the NSF signal and the
DIS signal inform the functions of the facsimile apparatus at the
destination terminal to the source terminal. The CED, NSF and DIS signals
are produced by the communication controller 16. In response to the NSF
and DIS signals, the facsimile apparatus at the source terminal sends a
non-standard facilities set-up signal (NSS) to the facsimile apparatus at
the destination terminal informing of the condition that the facsimile
transmission will be made.
FIG. 4 shows the structure of the NSS signal. In the present embodiment,
the NSS signal comprises a 128 bit digital data, wherein the first 16 bits
or 2 bytes are used for statement that this signal has a structure in
compliance with the CCITT protocol, and a manufacturer's code is
represented in the column from a bit 17 to a bit 24 in a form of eight bit
or one byte data. Further, in the column from a bit 25 to a bit 32, a
statement that the signal is the NSS signal is made in a form of eight bit
or one byte data.
After a bit 33, various of facsimile transmission conditions are specified
up to the last bit at a bit 128, wherein the type of the transmission
medium used for facsimile transmission is specified in a form of two-bit
data in bits 122 and 123. When the facsimile transmission is to be made by
the usual wired telephone network from the facsimile apparatus 1 at a
fixed station such as office, both of the bits 122 and 123 are set to
zero. When the facsimile transmission is to be made from the facsimile
apparatus 4 at a mobile station such as automobile, a digit "1" is set in
the bit 122. Further, when the facsimile transmission is to be made from a
facsimile apparatus coupled to the public telephone network via an
acoustic coupler as will be described later with reference to a second
embodiment of the present invention, a digit "1" is set in the bit 123.
The foregoing NSS signal is produced by the communication controller 16 of
the facsimile apparatus at the source terminal under control of the system
controller 18. Thus, the communication controller 16 of the facsimile
apparatus 1 in the fixed station sets the digit "0" in the bits 122 and
123 when sending a facsimile transmission, while the communication
controller 16 of the facsimile apparatus 41 in the mobile station sets the
digit "1" in the bit 122 when sending a facsimile transmission. As long as
the facsimile apparatus 1 is the fixed type machine and used always in
combination with the fixed station in the office or as long as the
facsimile apparatus 41 is used always in combination with the automobile
telephone, the foregoing setting of the digit in the bit 122 in the NSS
signal is unconditional.
Next, the operation of the facsimile apparatus at the destination terminal
will be described with reference to FIG. 5 showing an operation of the
stationary type facsimile apparatus 1 under control of the system
controller 18 when receiving a facsimile transmission. In this case, there
are two possibilities that the facsimile transmission is made from another
stationary type facsimile apparatus operating at a fixed station or the
facsimile transmission is made from a facsimile apparatus operating in a
mobile station such as automobile telephone. The case that the facsimile
apparatus 1 receives facsimile transmission from a facsimile apparatus
using the acoustic coupler will be considered later. As already described
with reference to the prior art, the quality of facsimile transmission
from the mobile station is significantly inferior to that from the fixed
station and it is desirable to change the threshold discriminating whether
the facsimile transmission is acceptable or not in accordance to the type
of the transmission medium used.
In a step 101 following the establishment of connection between the source
terminal and the destination terminal, the facsimile apparatus 1 sends the
CED, DIS and NSF signals to the source terminal and receives the NSS
signal in a step 102. As already described, this NSS signal carries in its
bit 122 the data indicating that the facsimile transmission is made from a
fixed station via a wired transmission line or from a mobile station via a
wireless transmission line, and the system control part 18 discriminates
whether the facsimile transmission is made via the wired transmission line
or not on the basis of the state of the bit 122 of the received NSS
signal.
Next, in a step 103, the facsimile apparatus 1 receives a modem training
signal TCF from the source terminal and performs a predetermined modem
training of the basis of the TCF signal in a step 103. When the modem
training is completed successfully, a CFR signal indicative of completion
of modem training is sent back to the source terminal.
After the step 103, an image information PIX for one page document is
received in a step 104 and the received PIX is line sequentially decoded
one line by one line while monitoring the transmission error according to
the predetermined, known procedure. Such a procedure is well established
and the description thereof will be omitted. At the same time, the number
of error lines that involved transmission error is counted up while
carrying out recording of the received image of the lines which are free
from transmission error sequentially on a recording sheet.
In a step 105, a discrimination is made, on the basis of the bit 122 of the
received NSS signal whether the facsimile transmission is made from a
mobile station via a radio wave transmission line or not. If the result of
discrimination is NO indicating that the facsimile transmission is made
from a facsimile apparatus at a fixed station via a wired transmission
line, an error discrimination is made in a step 106 in which it is decided
that the facsimile transmission is unacceptable when the number of error
lines involving the error reaches ten or more. This ten-line threshold for
discriminating the failure of facsimile transmission is commonly used in
the current facsimile apparatus used in the fixed stations such as office.
If the result of discrimination in the step 106 is NO indicating that the
quality of facsimile transmission is acceptable, a signal designated as a
MCN signal is sent to the source terminal informing the facsimile
apparatus at the source terminal of the successful reception of the
facsimile transmission. On the other hand, when the result of
discrimination in the step 106 is YES indicating that there are ten or
more error lines containing transmission error and the quality of
facsimile transmission is unacceptable, the RTN signal is sent to the
source terminal in a step 108 and the facsimile transmission is
terminated. This threshold of ten error lines in the discrimination step
of 106 is currently used in the conventional facsimile apparatus as
already noted and thus, the foregoing process is identical to the process
performed in the currently used fixed type facsimile apparatus for office
use.
When it is discriminated in the step 105 that the facsimile transmission is
made from a mobile station on an automobile, a discrimination is made
subsequently in a step 109 if the number of error lines involving the
transmission error has reached or exceeded 50 lines or not. If yes, the
RTN signal 108 is sent to the source terminal facsimile on the mobile
station in the foregoing step 108 and the transmission is disconnected. In
response to this, the facsimile apparatus at the source terminal displays
a message such as "RE-SEND THE DOCUMENT" to the operator at the source
terminal.
Thus, it will be understood that the threshold number of error lines used
for discriminating the failure of facsimile transmission is now increased
and a less stringent standard is imposed as to the quality of the
facsimile transmission when the facsimile transmission is made from a
mobile station.
When the result of discrimination in the step 109 is NO indicating that the
number of error lines involving transmission error in one page is less
than fifty, it is further discriminated in a step 110 whether there are
error lines in continuation for twelve lines or more or not. If yes, the
RTN signal is sent in the step 108 and the transmission is disconnected
similarly to the case where there are fifty or more error lines involving
the transmission error. Only when the number of such error lines involving
the transmission error is less than 50 and at the same time there are no
continuous appearance of such error lines in succession for twelve lines
or more, the facsimile transmission is accepted satisfactory and the MCN
signal is sent in the step 107. Thus, even though the standard for
discriminating the failure of facsimile transmission is lowered in the
case of receiving facsimile transmission from mobile stations, certain
standard is still maintained and the minimum quality of facsimile
transmission is guaranteed.
By choosing the threshold number of error lines for discriminating the
transmission failure for the case of facsimile transmission from mobile
stations to be fifty as described, error lines of about 5% are allowed
when the document to be transmitted is a standard A4 size document
transmitted with a line density of 3.85/mm in an ordinary mode. Note that,
in such a case, the document contains about 1140 lines in one page and the
foregoing 50 allowable error lines corresponds to about 5% of the total
line. PG,21
In the usual document, each letter has a size of about 5 mm.times.5 mm.
When the line density is set to the foregoing 3.85/mm, the letter of this
size includes about 13 lines. Thus, by setting the threshold for the case
of continuous appearance of the transmission errors to twelve lines as in
the step 110, problem such as the acceptance of total dropout of one line
of letters in the document without knowing that such a dropout has occured
is positively avoided. When such a drop out occurs, there are cases that
the operator at the destination terminal cannot notice the error from the
received document, as the entire one document line is dropped out. In the
facsimile apparatus of the present invention, the request is made to the
operator at the source terminal to re-transmit the document when such a
case arises.
When receiving the facsimile transmission by a facsimile apparatus at a
mobile station, the foregoing step 105 as well as the step 106 are
omitted, as the wireless transmission line is used always in such an
apparatus.
FIG. 6 shows an example of the facsimile system used in the mobile station.
Thus, the system in FIG. 6 corresponds to the facsimile system of FIG. 2B.
In the drawing, the parts corresponding to the parts already described
with reference to preceding drawings are given identical reference
numerals and the description thereof will be omitted.
Referring to FIG. 6, the interface unit 42 includes transformers 421a and
421b for impedance matching, a relay switch 422, and a serial signal
transfer/detection unit 423. The automobile telephone apparatus 43
comprises a tranceiver set 43a 10 and a handset 43b. The interface unit 42
is connected to the tranceiver set 43a and to the handset 43b, and the
image data to be transmitted is sent to the tranceiver set 43a from the
modem 15 via the transformer 421a and the relay switch 422. When receiving
the transmitted image data, the image data is sent from the tranceiver set
43a to the modem 15 via the relay switch 422 and the transformer 421b.
The serial signal transfer/detection unit 423 receives a predetermined
serial down signal SD from the tranceiver set 43a and transfers the signal
SD to the handset 43b. Further, the unit 423 receives a predetermined
serial up signal SU from the handset 43b and transfers the signal SU to
the tranceiver set 43a. Further, the serial signal transfer/detection unit
423 sends a predetermined on-hook signal OH, call-in signal CC and a
ringing signal RI to the facsimile apparatus 41. The foregoing
construction and function of the serial signal transfer/detection unit 423
is known and not related to the subject matter of the present invention.
Thus, further description with regard to the unit 423 will be omitted.
In the interface unit 42, it should be noted that there is provided a light
emitting diode LED 424. When the facsimile apparatus 41 is connected to
the interface unit 42, a corresponding photo-sensor 50 provided in a
connector assembly of a cable which is connected to the facsimile
apparatus for connection to the interface unit 42 is engaged with the LED
424, and there is formed a photocoupler PC1 as shown in FIG. 6. When the
facsimile apparatus 41 is connected to the interface 42, the photo-sensor
produces an output signal PC which assumes a low level state while when
the facsimile apparatus 41 is dismounted from the interface unit 42, the
output signal PC of the photo-sensor 50 becomes high. Thus, the
photocoupler PC1 discriminates the physical connection of the facsimile
apparatus to the interface unit 42.
In response to the low-level output signal PC which is supplied to the
system controller 18 via an input/output unit 58 which is connected on the
one hand to the photosensor 50 and further to the system bus 10, the
system controller 18 controls the communication controller 16 such that
the digit "1" is set in the bit 122 of the NSS signal to be sent to the
destination terminal. In response thereto, the facsimile apparatus at the
destination terminal can know that the facsimile transmission is made from
a mobile station via a wireless transmission line.
The facsimile apparatus 41 of FIG. 6 is suitable for a portable facsimile
apparatus in that the apparatus can be dismounted from the interface unit
42 and connected to the wired transmission line via a network controller
provided separately when the facsimile apparatus 41 is used outside of the
automobile. In such an apparatus, it is possible to discriminate whether
the facsimile apparatus 41 is connected to the automobile telephone
apparatus 43 or to the wired transmission line on the basis of the state
of the signal PC. Thus, it becomes possible to control the digit in the
bit 122 of the NSS signal depending on the state of the PC signal.
Next, a second embodiment of the present invention will be described with
reference to FIG. 7 wherein an acoustic coupler is used for connecting the
facsimile apparatus 1 to the wired transmission line. In FIG. 7, the parts
described already with reference to preceding drawings are given identical
reference numerals and the description thereof will be omitted.
Referring to FIG. 7, the facsimile apparatus 1' comprises an acoustic
coupler interface 19 which is adapted to be connected to an acoustic
coupler 5 via a cable 5a. This acoustic coupler 5 is mounted on a handset
of a telephone and establishes a communication with the public telephone
network by exchanging information signals between the handset in a form of
acoustic signal.
The acoustic coupler interface 19 is connected to the modem 15 and sends
the signal received by the acoustic coupler 5 to the modem 15 and further
sends the output signal of the modem 15 to the acoustic coupler 5.
Further, the acoustic coupler interface 19 is connected to the system
controller 18 for providing a signal AC indicating that the acoustic
coupler is used to the system controller 18. This signal AC may be
produced in response to the connection of the cable 5a to the acoustic
coupler interface 19. The detection whether the cable 5a is connected to
the interface 19 may be made for example by a photocoupler PC2 similar to
the photocoupler PC1 described in FIG. 6. Thus, when the cable 5a is
connected to the facsimile apparatus 1', a photo-sensor similar to the
photo-sensor 50 and coupled to an LED similar to the LED 424 and forming
the photocoupler PC2, produces the signal AC having the low level state
indicating that the acoustic coupler 5 is used. When the cable 5a is not
connected, the signal AC assumes a high-level state. As the construction
of the photocoupler PC2 is identical to that of the photocoupler PC1, the
illustration and description will be omitted. Alternatively, the signal AC
may be given by the acoustic coupler 5 when the power switch of the
acoustic coupler 5 is turned on.
In response to the signal AC detecting the use of the acoustic coupler 5,
the communication controller 16 sets the digit "1" in the column or bit
123 of the NSS signal, and on the basis of this NSS signal, the facsimile
apparatus at the destination terminal discriminates that the facsimile
transmission is sent via transmission path involving an acoustic coupler
by performing the steps shown in FIG. 5 except that the discrimination
step 105 discriminates the use of the acoustic coupler by watching the bit
123 of the NSS signal.
By monitoring the bits 122 and 123 of the NSS signal, it is possible to
discriminate whether the facsimile transmission is sent via the wireless
transmission path or via the path involving the acoustic coupler. In such
a case where the use of wireless transmission path and the use of acoustic
coupler is discriminated on the basis of the bit 122 and the bit 123 of
the NSS signal, it is possible to change the threshold number of error
lines as shown in FIGS. 8A and 8B in response to the wireless transmission
path and the acoustic coupler. In these drawings, the steps already
described with reference to FIG. 5 are given identical reference numerals
and the description thereof will be omitted.
In the process of FIG. 8A, a modified step 105' is used to discriminate
whether the facsimile transmission is made via the wired transmission path
or wireless transmission path or via the transmission path involving
acoustic coupler. When it is discriminated that the transmission is made
via the wired transmission path or via the wireless transmission path, the
steps 106-110 are performed as already described. When it is discriminated
that the facsimile transmission is made via the transmission path
involving the acoustic coupler, a step 109' is performed where the number
of error lines has reached thirty or not. If YES, the step 108 is
performed where the RTN signal is sent to the facsimile apparatus at the
source terminal and the facsimile apparatus at the source terminal
requests re-trial of facsimile transmission to the operator similarly to
the foregoing case. When the result of discrimination is NO, it is further
discriminated in a step 110' whether there are consecutive eight or more
error lines or not. If YES, the step 108 is performed and the RTN signal
is sent to the facsimile apparatus as the source terminal while if NO, the
step 107 is performed and the MCF signal is sent to the source terminal
for informing of the successful reception of that page.
By changing the threshold number of error lines in the steps 109 and 109'
or in the steps 110 and 110', the difference in the transmission quality
between the wireless transmission path and the transmission path involving
the acoustic coupler can be taken into consideration with respect to the
allowable quality of the facsimile transmission.
Next, a modification of the process of FIG. 5 or FIG. 8A will be described
with reference to FIG. 9.
The process of FIG. 9 represents the content of the process performed in
the step 104 and comprises a first step 201 where the total number of
error lines N.sub.E in the page to be received is initialized, a second
step 202 for receiving one line of transmitted image, a third step 203 for
detecting the error in the received line, a fourth step 204 for counting
up the total number of error lines, and a step 205 for discriminating if
the received line is the end of that page. If the result of discrimination
is the step 205 is NO, the step 202 and the steps following thereto are
performed repeatedly until the last line is received.
When the result of discrimination in the step 203 is NO indicating that the
just received line is a line successfully received, a discrimination is
made in a step 206 whether a predetermined number of successive lines such
as N successive lines has been received successfully and if YES, the
number N.sub.E is reduced by one within the range that N.sub.E is a
positive integer in steps 207 and 208. If the result of discrimination in
the step 206 is NO, the step 205 is performed and further error detection
for the subsequent line is continued.
By reducing the total number of errors upon successful reception of a
number of consecutive lines, the facsimile transmission is rescued from
being discarded, as such a facsimile transmission may still be
intelligible even when the actual total number of lines has exceeded fifty
because of the noises concentrated at the beginning of the facsimile
transmission. Thus, the operator at the source terminal can save the
additional trial of transmitting the document.
As a modification of the process of FIG. 5, one may omit either the step
109 for discriminating the transmission failure on the basis of the total
number of error lines or the step 110 for discriminating the transmission
failure on the basis of the consecutive appearance of the error lines. A
same modification is applicable also for the case of the process of FIGS.
8A and 8B.
Further, the present invention is not limited to the embodiments described
heretofore but various variations and modifications may be made without
departing from the scope of the invention.
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